Synchronization of multiple video and graphic sources with a display using a slow PLL approach
First Claim
1. A method of synchronization of one or more video sources to a display, comprising the steps of:
- generating a clock signal having a frequency and a phase,buffering each of said video sources via one or more memory devices,selecting one of said video sources as a primary source,adjusting said clock frequency in dependence upon said primary source,synchronizing the display to said clock frequency and clock phase, and,extracting each of said video sources from said memory devices in dependence upon said clock frequency and clock phase,characterized in that said adjusting of the clock frequency is performed in such a manner that no discernable discontinuities are introduced in the clock frequency, nor in the clock phase.
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Accused Products
Abstract
A slow Phase Locked Loop (PLL) is utilized to prevent an abrupt change to a video display containing multiple images, when the source of the synchronization is changed. Such displays include Picture in Picture (PIP) television systems and computer displays. By appropriate buffering and memory management, visual disruptions can be minimized by slowly synchronizing the display synchronization signals to the new synchronization source. The slow synchronization also produces a less disruptive visual image when the source, or channel, of a single image display is changed, and allows for smooth visual transitions on displays having inertial elements, such as color wheels.
102 Citations
12 Claims
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1. A method of synchronization of one or more video sources to a display, comprising the steps of:
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generating a clock signal having a frequency and a phase, buffering each of said video sources via one or more memory devices, selecting one of said video sources as a primary source, adjusting said clock frequency in dependence upon said primary source, synchronizing the display to said clock frequency and clock phase, and, extracting each of said video sources from said memory devices in dependence upon said clock frequency and clock phase, characterized in that said adjusting of the clock frequency is performed in such a manner that no discernable discontinuities are introduced in the clock frequency, nor in the clock phase. - View Dependent Claims (10)
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2. An apparatus for synchronization of one or more video sources to a display, comprising:
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means for generating a clock signal having a frequency and a phase, means for buffering each of said video sources via one or more memory devices, means for selecting one of said video sources as a primary source, means for adjusting said clock frequency in dependence upon said primary source, means for synchronizing the display to said clock frequency and clock phase, and, means for extracting each of said video sources from said memory devices in dependence upon said clock frequency and clock phase, characterized in that said means for adjusting the clock frequency produces no discernable discontinuities in the clock frequency, nor in the clock phase. - View Dependent Claims (3, 4, 8, 11)
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5. An apparatus for synchronization of one or more video sources to a display, each of said video sources having an associated source frame rate, and said display having a video display rate and a video display phase, said apparatus comprising:
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a buffer associated with each of said video sources a sync control comprising; means for selecting one of said video sources as a primary signal, and, means for generating a display synchronization signal and a memory synchronization signal in dependence upon said primary signal, said display synchronization signal controlling said video display rate; a memory control associated with each of said buffers comprising; means for writing the associated video source into the associated buffer in dependence upon the associated source frame rate, and, means for reading the associated buffer in dependence upon the memory synchronization signal to form a buffered video signal; a mixer for combining each of said buffered video signals to form a composite video signal having a composite frame rate equal to said video display rate, and a composite video phase equal to said video display phase, characterized in that said synchronization signal generating means reacts gradually to said primary signal so as not to introduce an abrupt change in the video display rate, the video display phase, the composite frame rate, nor the composite video phase. - View Dependent Claims (6, 7, 9, 12)
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Specification